1. Field of the Invention
The present invention relates to a linkage mechanism between a zoom lens barrel unit and a zoom member, a camera incorporating a linkage mechanism between a zoom lens barrel unit and an illumination range-changing device that changes the range of illumination with illuminating light and between the zoom lens barrel unit and a zoom finder device that changes the magnification of a finder optical system, and a method of assembling the illumination range-changing device and the zoom finder device.
2. Description of the Related Art
Conventionally, some cameras incorporate a linkage mechanism between a zoom strobe device that changes the range of illumination with strobe light in a manner interlocked with the motion of a drive ring for driving a zoom lens barrel unit, and a zoom finder device that changes the magnification of a finder optical system in a manner interlocked with the motion of the drive ring (see e.g. Japanese Laid-Open Patent Publication (Kokai) No. H09-211556).
A description will be given of a linkage mechanism of the above-mentioned kind with reference to FIG. 26, which shows, in cross-section, main components of a conventional linkage mechanism between a zoom strobe device and a zoom finder device.
As shown in FIG. 26, the linkage mechanism has a rotation axis parallel to the direction of motion (direction of the optical axis) of an objective lens 302 of the zoom finder device, and includes a zoom finder cam ring 301 that performs zooming of the zoom finder device, and a strobe cam ring 401 that changes the angle of illumination by the zoom strobe device.
An outer peripheral gear 101 provided on the zoom lens barrel unit transmits the rotation of the zoom lens barrel unit to the finder cam ring 301 via a transmission gear train 201, and the finder cam ring 301 rotates about its rotation axis. A finder magnification-changing cam, not shown, is provided on the periphery of the finder cam ring 301, and a cam pin 302a protruding from the objective lens 302 is in contact with the finder magnification-changing cam, whereby the objective lens 302 is moved in the direction of the optical axis, following the profile of the cam along with rotation of the finder cam ring 301 to zoom an image in the view finder.
Further, a gear 301a is provided at an end of the finder cam ring 301, and the gear 301a meshes with a gear 401a provided at an end of the strobe cam ring 401. With this arrangement, when the finder cam ring 301 rotates, the strobe cam ring 401 rotates about its rotation axis in a manner interlocked with the rotation of the finder cam ring 301. The strobe cam ring 401 has a strobe illumination angle-changing cam, not shown, formed on the outer periphery thereof, and a cam pin 402a protruding from a base member of a strobe flash section 402 is in contact with the strobe illumination angle-changing cam. With this arrangement, the strobe flash section 402 is moved in the direction of the optical axis, following the cam profile of the strobe illumination angle-changing cam along with rotation of the strobe cam ring 401, to thereby vary the angle of illumination with strobe light.
However, in the construction of the conventional linkage mechanism shown in FIG. 26, the rotation of the zoom lens barrel unit is transmitted to the finder cam ring 301 via the transmission gear train 201, and hence the influence of play due to backlash of the gears is large, which makes it difficult to control the position of the objective lens 302 and that of the strobe flash section 402 with high accuracy. Further, it is necessary to reduce the rotational speed of the zoom lens barrel unit in transmitting the rotation to the finder cam ring 301, and hence it is necessary to provide a plurality of gears including the transmission gear train 201. As a result, the construction of a drive mechanism for driving the objective lens 302 and the strobe flash section 402 becomes complicated, which makes it difficult to reduce the size of the camera. Further, it is necessary to incorporate the finder magnification-changing cam and the strobe illumination angle-changing cam in a state in phase with each other, which makes it very difficult to assemble the camera.
Further, a camera provided with a zoom finder device which changes the magnification of a finder optical system in a manner interlocked with the zooming motion of the zoom lens is disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2004-145044.
A description will be given of the zoom finder device with reference to FIGS. 27 and 28. FIG. 27 is a cross-sectional view showing a drive mechanism of the conventional zoom finder device, and FIG. 28 is a developed view of a cam ring appearing in FIG. 27.
As shown in FIG. 27, the camera has a drive gear 501 to which the rotation of a zoom motor, not shown, for causing the zoom lens to perform a zooming operation, is transmitted via a gear system. The drive gear 501 meshes with an inner peripheral gear 601a formed on a drive ring 601, and the drive gear 501 drives the drive ring 601 for rotation. The drive ring 601 has an outer peripheral gear 601b formed in the outer peripheral surface of the drive ring 601, and the outer peripheral gear 601b meshes with a transmission gear 701 that transmits a driving force to the zoom finder device. The rotation of the transmission gear 701 is transmitted to the cam ring 702. That is, the driving force for the zooming operation is transmitted to the zoom finder device side.
The cam ring 702 has two objective lens cams 702a and 702b formed thereon as shown in FIG. 28. Cam pins 801 and 802 protruding from associated objective lenses, not shown, are abutted against the cams 702a and 702b. A finder base 901 holds the objective lenses in a manner they are movable in the direction of the optical axis. When the cam ring 702 is rotated, the objective lens are moved in the direction of the optical axis, following the cam profiles of the cams 702a and 702b, whereby an image viewed in the view finder can be zoomed. Moreover, the cams 702a and 702b are formed such that areas (circled area RWa, RWb, RTa, and RTb in FIG. 28) corresponding to WIDE (wide angle) ends and TELE (telephoto) ends have no slope, and hence they each can stably obtain a desired magnification position without being adversely affected by the backlash of the gears or the like.
However, in a path on the cam 702a from a magnification area which has a varying slope to the WIDE end or the TELE end having no slope, there are slope-transition points, and when the objective lens passes the slope-transition points during zooming, jitter of an image occurs.
To prevent jitter of an image from occurring, separate component parts are required for imparting a biasing force to the objective lens in an opposite direction to the direction of rotation when the objective lens passes the slope-transition points.